The father-son duo won all but one stage of the rally's classic section in their 1980 Toyota Celica RA40 to beat their nearest rival by more than five-and-a-half minutes.
Bates said Harry had delivered his pace notes efficiently despite it being his first competition rally.
"I didn't expect him to do so well," he said. "I had hoped it would be a good learning experience but he really impressed me and showed he did his homework.
"The conditions were pretty tough too with overnight rain making the roads quite slippery."
Harry prepared for the rally under the tutelage of Bates' long-time co-driver and four-time national champion Coral Taylor, who was unable to participate in the event due to a commitment in Europe.
The 18-year-old said Taylor's expert guidance prepared him for what was an initially daunting but memorable experience.
"I can't thank Coral enough for all she did," he said. "I went into it with a good idea of preparing and calling out pace notes and just generally being organised.
"Even still, I felt a little bit of pressure when I got in the car on Saturday morning!"
He said the slipperier surface on Sunday only added to the exhilaration of riding as a passenger in the thoroughbred Celica with his four-time national champion father.
"It was great fun and pretty amazing to be out in the car with dad," he said. "I did grab the door handle pretty tight a few times though on Sunday!"
Harry, who will finish high school this year, said he hoped to get another opportunity to co-drive, but he was not about to take Taylor's seat.
"After 20 years and four national championships it's going to be a bit hard to do that!" he said.
"I would also like to get into the driving side so I'll chat to dad about that, too."
Sunday's heat of the International Rally of Queensland was marred by tragedy when another car crashed during stage 14, killing the co-driver and severely injuring the driver.
Taylor will reunite with Bates for Rally Australia on September 12 to 15.
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